The correct answer is: A. Oxidation followed by settling and filtration.
Iron and manganese are common water pollutants that can cause a variety of problems, including discoloration, staining, and taste and odor problems. They can also be harmful to human health.
There are a number of methods that can be used to remove iron and manganese from water. One common method is oxidation followed by settling and filtration. In this process, the iron and manganese are oxidized to their ferric and manganic forms, which are then precipitated out of solution. The precipitate is then removed by filtration.
However, this method is not effective for removing all
forms of iron and manganese. For example, it is not effective for removing iron and manganese that are present in organic matter. In these cases, other methods, such as ion exchange or lime soda softening, may be necessary.Ion exchange is a process in which ions in solution are exchanged for ions on a resin. In the case of iron and manganese removal, the resin is typically a strong base anion exchange resin. The iron and manganese ions are exchanged for chloride ions, which are then removed from the water by rinsing the resin with a brine solution.
Lime soda softening is a process in which calcium and magnesium ions in solution are removed by precipitation. In this process, lime (calcium oxide) and soda ash (sodium carbonate) are added to the water. The calcium and magnesium ions react with the lime and soda ash to form calcium carbonate and magnesium hydroxide, which are then precipitated out of solution.
Both ion exchange and lime soda softening are effective methods for removing iron and manganese from water. However, they are more expensive than oxidation followed by settling and filtration. The choice of method will depend on the specific characteristics of the water and the desired level of treatment.